Dial for a universal watch

ABSTRACT

A dial includes a ring in the form of an annular plate, a central disc mounted in a concentric and essentially coplanar manner with respect to the ring, the diameter of the central disc being less than the internal diameter of the ring so as to form an annular area between the two, and a transparent part which covers the annular area. Further, the transparent part is fixed to the central disc and to the ring to secure these elements to each other. The dial can be used in a timepiece with a universal time display and makes it possible to mount a twenty-four hour disc underneath the dial, and to view the markings on the twenty-four disc through the transparent part.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to European Patent Application No.19163830.3 filed on Mar. 19, 2019, the entire disclosure of which ishereby incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to horology, more particularly to a dialthat can be used in a timepiece with a universal time display.

STATE OF THE ART

A universal watch can simultaneously display the current time indifferent time zones in the world. Such a watch usually comprises afixed dial, hour and minute hands which are driven and move above thedial in the clockwise direction, at a rate of one revolution in 12 hoursand one revolution in 1 hour respectively, a twenty-four hour disc and adisc concentric to the dial and to the twenty-four hour disc bearing thenames of the cities or global locations that represent the differenttime zones. The twenty-four hour disc is connected to the hour hand by agear, in order to rotate at a rate of one revolution per 24 hours in theanticlockwise direction, the time of a location being indicated by thedivision of the twenty-four hour disc which is facing said location. Inmost cases, the dial and the disc bearing the names of the cities areparts that are independent of one another, the dial generally beinglocated at the centre, integral with the movement, and the twenty-fourhour disc and the city disc surrounding the central dial in successionand in a coplanar manner. Such a design has the particular drawback ofrequiring the upper part of the movement to be adapted, in particular inorder to arrange the dial.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a dial which doesnot suffer from the drawbacks identified above. This object is achievedby a dial according to the annexed claims. The invention also concerns atimepiece, such as a watch, equipped with a dial according to theinvention. A dial according to the invention comprises a ring in theform of an annular plate, a central disc mounted in a concentric andessentially coplanar manner with respect to the ring, the diameter ofthe central disc being less than the internal diameter of the ring toform an annular area between the two, and a transparent part whichcovers said annular area. Further, the transparent part is fixed to thedisc and to the ring to secure these elements to each other. The dialcan be used in a timepiece with a universal time display and makes itpossible to mount a twenty-four hour disc in a simple way on themovement beneath the dial, and to view the markings on the twenty-fourdisc through the transparent part.

Specific features and advantages of the present invention will appear inthe following description of preferred embodiments, given by way ofnon-limiting example with reference to the annexed drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 represents a front view of a watch dial according to anadvantageous embodiment of the invention.

FIG. 2 represents a sectional view along section A-A shown in FIG. 1 .

FIG. 3 represents an exploded view of the components of the dial shownin FIGS. 1 and 2 .

FIG. 4 represents a watch equipped with the dial represented in FIG. 1 .

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Dial 1 represented in FIGS. 1 and 2 comprises three parts secured toeach other to form a single integral part. The dial can be used for awristwatch. Dial 1 comprises a flat ring 2, preferably made of metal, inthe form of an annular plate having an external diameter D1 and aninternal diameter D2. In the embodiment of the Figures, ring 2 hastwelve indices 3 affixed to the upper surface of ring 2 by mounting feet4 (see FIG. 2 ). The ‘upper surface’ means here the surface intended tobe positioned facing the watch crystal and the ‘lower surface’ means theopposite surface. The positions of indices 3 indicate the positions ofthe hours from 1 to 12. Ring 2 also bears the names of 24 citiesregularly distributed around the edge of ring 2, the names of the citiescorresponding to the 24 time zones of the world. The names are etched inthe upper surface of ring 2 and on the surface of an additional ring 5having an inclined surface with respect to the plane of ring 2. Theadditional ring is secured to said upper surface of ring 2 by mountingfeet 6.

In the specific case represented in FIG. 1 , ring 2 also includes anaperture 12 arranged at 6 o'clock for displaying the date. Ring 2 ismade of an opaque material, for example, a metal alloy, such as CuZn33.Concentrically with respect to ring 2, and essentially in the same planeas ring 2, there is mounted a central, preferably metal disc 7, alsomade of an opaque material, for example titanium, and comprising acentral hole 8 for the passage of rotating arbors which carry the hourand minute hands of a watch. The diameter D3 of central disc 7 is lessthan the internal diameter D2 of ring 2, which leaves an annular area 9visible between disc 7 and ring 2. Said annular area 9 is covered by apart 10 made of a transparent material, such as PMMA (poly methylmethacrylate) or sapphire.

In the specific case represented in the Figures, transparent part 10also takes the form of a flat ring and has a central opening 11positioned concentrically with respect to central disc 7 (FIG. 3 ).Opening 11 is dimensioned such that transparent part 10 covers anannular portion 15 located on the periphery of the lower surface of disc7. On the opposite side to opening 11 in the radial direction,transparent part 10 covers an annular portion 16 which is on the innerperiphery of the lower surface of ring 2. Transparent part 10 is bondedto said surface portions 15 and 16, so as to keep ring 2 and disc 7secured to each other. Seen in a plan view in FIG. 1 , dial 1 thuscomprises an opaque ring 2, an opaque central disc 7, and an annularaperture between disc 7 and ring 2.

The exploded view of FIG. 2 reveals the specific features of thisembodiment. It is seen that, on its lower surface, central disc 7 isprovided with a circular portion 17 extending in relief with respect toportion 15 which is covered by transparent part 10. The diameter ofrelief portion 17 corresponds to the diameter of opening 11, allowingtransparent part 10 to be positioned around relief portion 17. Further,relief portion 17 has a radial protrusion 18, configured to engage in aradial notch 19 arranged in inner edge 20 of transparent part 10, suchthat the assembly of transparent part 10 to disc 7 is only possible inone specific angular position of transparent part 10 with respect todisc 7.

It is also seen that the outer edge of transparent part 10 includesthree straight portions 25 arranged at equal angular distances aroundthe periphery of part 10, while the rest of the edge consists of threecurved portions 26 which are arcs of a circle. Annular portion 16 ofring 2, which will be covered by transparent part 10, is indented withrespect to the back surface of ring 2. Said annular portion 16 is alsoprovided with complementary straight portions 25′ and curved portions26′ which correspond to the straight and curved portions 25, 26 oftransparent part 10, allowing transparent part 10 to be positionedinside indented portion 16 by aligning straight portions 25, 25′ andcurved portions 26, 26′. In this embodiment, the lower surface of ring 2further comprises hollow areas 27 located on the periphery of portion 16and provided with threaded holes 28 arranged at the bottom of said areas27. Holes 28 are configured to receive mounting screws 29 designed toattach or participate in the attachment of transparent part 10 to ring2. Attachment is realized by the heads of mounting screws 29, which fitinto hollow areas 27, extending over the edge of part 10 when screws 29are tightened, to attach part 10 to ring 2.

The assembly of dial 1 shown in the Figures is preferably carried out intwo steps. First, transparent part 10 is assembled on central disc 7, byaligning protrusion 18 and notch 19 and by placing part 10 around reliefportion 17 and in contact with surface portion 15, after applying anadhesive to at least one of the contact surfaces. An adhesive that canbe used for a titanium disc 7 and a PMMA transparent part 10 is APMTechnica Epsilon 2103 adhesive. The assembly formed by part 10 and disc7 is then fixed to the indented surface portion 16 of ring 2, byapplying another adhesive to at least one of the contact surfaces oftransparent part 10 and of portion 16 of ring 2. Next, mounting screws29 are tightened in threaded holes 28, preferably after the applicationof an adhesive to the surface of hollow areas 27 in which the screwheads will be housed.

The adhesive used between transparent part 10 and ring 2 may be of thesame type as the adhesive used between part 10 and central disc 7.Alternatively, a weaker adhesive is used between transparent part 10 andring 2 than between part 10 and disc 7. A ‘weaker’ adhesive means anadhesive which provides lower adhesion when the assembly is subject to adetermined shock.

According to yet another embodiment, transparent part 10 is not bondedto ring 2 but is attached to ring 3 simply by mounting screws 29.

According to yet another embodiment, mounting screws 29 are omitted andtransparent part 10 is bonded to disc 7 and to ring 2. In this latterembodiment, the adhesive used between transparent part 10 and ring 2 canbe as strong as the adhesive used between part 10 and disc 7, or weaker.

The embodiments in which a weaker adhesive is used between transparentpart 10 and ring 2 than between part 10 and disc 7, or in whichtransparent part 10 is attached to ring 2 simply by mounting screws 29,have the advantage of improving the shock resistance of the dial, owingto the fact that the deformability of transparent part 10 increasescompared to ring 2. Dome-shaped deformation of the dial (‘umbrellaeffect’), in particular, which may cause the hands to come loose, islimited in the event of shocks.

A watch provided with the dial described above is represented in FIG. 4. The watch has hour and minute hands 30 and 31, which move above thedial to indicate the time and which are driven in rotation in aconventional manner by a timepiece movement (not represented), and anannular twenty-four hour disc 32, also driven in rotation by saidmovement which moves underneath dial 1. Twenty-four hour disc 32 isprovided with 24 markings regularly distributed over its surface. Themarkings are aligned with the annular area between central disc 7 andring 2, so that these markings are seen through the aperture created bytransparent part 10. Twenty-four hour disc 32 is driven and corrected byknown mechanisms generally simultaneously with the hour and minutehands. The watch also includes an annular date disc aligned withaperture 12, also driven in a known manner. Central disc 7 can also beprovided with a decoration, by etching for example. Typically, centraldisc 7, made, for example, of titanium, can be decorated by means of anultrashort pulse laser, typically a femtosecond laser, which makes itpossible to sculpt nanostructures on the surface of the disc whichselectively reflect certain wavelengths of visible light and thus allowcolouring.

Those skilled in the art understand that variants of certain features ofthe dial described above are within the scope of the invention.Transparent part 10 could take the form of a solid disc instead of aring. Instead of, or in addition to adhesives and mounting screws, othermeans of attachment could be used to secure transparent part 10 to disc7 and/or to ring 2. Transparent part 10 could be fixed to the uppersurface instead of the lower surface of disc 7 and/or of ring 2.

The invention claimed is:
 1. A dial for a timepiece, the dialcomprising: a flat ring made of opaque material, having an externaldiameter and an internal diameter, the ring having an upper surface anda lower surface; a central disc made of opaque material having adiameter which is less than the internal diameter of the ring, thecentral disc being positioned concentrically with respect to the ringand essentially coplanar with the ring, such that an annular area iscreated between the disc and the ring, the central disc having an uppersurface and a lower surface respectively oriented like the upper surfaceand the lower surface of the flat ring; and a part made of transparentmaterial which covers the annular area and which is fixed to the centraldisc and to the ring, in order to join the ring and the central disc toeach other, while creating an annular aperture between the disc and thering, wherein the transparent part covers at least one portion of theupper surface of the central disc from above or the lower surface of thecentral disc from below.
 2. The dial according to claim 1, wherein thetransparent part is fixed to the central disc by bonding the transparentpart to said surface portion.
 3. The dial according to claim 2, whereinsaid surface portion of the central disc covered by the transparent partis an annular portion which is on the periphery of the upper or lowersurface of the central disc.
 4. The dial according to claim 3, whereinthe transparent part has a flat annular shape, said part comprising acentral opening positioned concentrically with respect to the centraldisc, and dimensioned such that the transparent part covers said annularportion on the periphery of the upper or lower surface of the centraldisc.
 5. The dial according to claim 4, wherein the central discincludes a relief portion surrounded by the annular portion, the reliefportion being dimensioned such that the opening is positioned aroundsaid relief portion.
 6. The dial according to claim 5, wherein theopening and the relief portion are respectively provided with a radialprotrusion and a radial notch or vice versa, the protrusion beingconfigured to engage in the notch, in order to only allow assembly ofthe transparent part to the central disc in one angular position of saidpart with respect to the central disc.
 7. The dial according to claim 1,wherein the transparent part covers at least one portion of the upper orlower surface of the ring, and wherein the transparent part is fixed tothe ring by the bonding and/or screwing of the transparent part to saidsurface portion of the ring.
 8. The dial according to claim 7, whereinsaid surface portion of the ring covered by the transparent part is anannular portion which is on the inner periphery of the surface of thering.
 9. The dial according to claim 8, wherein said annular portion isin an indented position with respect to the rest of said surface of thering.
 10. The dial according to claim 9, wherein the outer edge of thetransparent part has geometric elements which allow angular alignment ofthe transparent part with respect to the ring, and wherein said annularportion includes alignment elements which correspond to the geometricelements on the outer edge of the transparent part.
 11. The dialaccording to claim 8, wherein the transparent part is fixed to the ringby at least a plurality of mounting screws comprising screw heads whichextend over the outer edge of the transparent part.
 12. The dialaccording to claim 1, wherein: the transparent part is fixed to thecentral disc by a first adhesive, the transparent part is fixed to thering by at least a second adhesive, and the second adhesive is weakerthan the first adhesive.
 13. The dial according to claim 1 wherein: thetransparent part is fixed to the central disc by a first adhesive, andthe transparent part is fixed to the rings by screws, without theapplication of adhesive.
 14. The dial according to claim 1, wherein thering comprises on its upper surface a plurality of names of globallocations which represent the time zones of the world.
 15. A timepiececomprising a dial, the dial comprising: a flat ring made of opaquematerial, having an external diameter and an internal diameter, the ringhaving an upper surface and a lower surface; a central disc made ofopaque material having a diameter which is less than the internaldiameter of the ring, the central disc being positioned concentricallywith respect to the ring and essentially coplanar with the ring, suchthat an annular area is created between the disc and the ring, thecentral disc having an upper surface and a lower surface respectivelyoriented like the upper surface and the lower surface of the flat ring;and a part made of transparent material which covers the annular areaand which is fixed to the central disc and to the ring, in order to jointhe ring and the central disc to each other, while creating an annularaperture between the disc and the ring, wherein the transparent partcovers at least one portion of the upper surface of the central discfrom above or the lower surface of the central disc from below.
 16. Thetimepiece according to claim 15, wherein the dial comprises on the uppersurface of the ring a plurality of names of global locations whichrepresent the time zones of the world, and wherein the timepieceincludes beneath the dial a twenty-four hour disc for marking theuniversal time with a plurality of markings distributed over thetwenty-four hour disc, and wherein the markings are aligned with theannular area between the disc and the ring of the dial.